Filter Backwash Water Research Articles

Cost-Benefit Analysis and Optimization of Semiconductor Processing Water Recycling Strategy

In this study, cost-benefit analyses based on life cycle assessment is applied to optimize the recycling of processing water for semiconductor factories. A representative 8-inch semiconductor wafer manufacturing plant is selected and seven existing or potential processing water-recycling sources were set, reverse osmosis (RO) reject, ultrafilter (UF) reject, multimedia filter (MMF), on-line analyzer drain, cation/anion (C/A) filter and merry-go-round (MGR) filter backwash water (including C/A sensor drain), wafer process organic drain and wafer process inorganic drain, marked as point 1 to 7, respectively. To sort the water-recycling sources in ascending order of the results of life cycle cost analyses, they were point 4, 5, point 2, 3, point 1, 7 and point 6, with life cycle the cost about 100,000$, 350,000$, 1000,000$ and 2000,000$, respectively. The order changed when they were sorted by their unit recycling-water costs; that was point 1, 2, point 5, point 3, 4 and point 7, with the unit recycling-water costs 0.2$/ton, 0.3$/ton, 0.4$/ton and 0.5$/ton, respectively. The analyses also evaluated the water recycling practice for various assumed unit tap water price. The optimal processing water recycling strategies based were proposed and corresponding optimal water-recycling rates were 24%, 64%, 81%, and 85% for water price 0.373$/ton, 0.578$/ton, 0.75$/ton and 0.945$/ton, respectively.

Study of Adsorbability of the Colloidal Particles from Different Stages of a Conventional Water Treatment Plant

The adsorbability of colloidal particles from different stages of a conventional water treatment plant was studied with the assistance of micro-membrane filtration experiment. The microfiltration (MF) performance and the scanning electron microscope (SEM) images of the foulants on membrane surface were investigated. The results showed that the particles in the ozonated water (OW) had the strongest adsorbability, and stronger than that in the clarified water (CW); and the particles in the sand filtrated water (SFW) had relatively weaker adsorbability than that in the raw water (RW). The particles in the sand filter backwash water (SFBW) were mainly consisted of detached aggregates and had weak attachment with the membrane surface.

Recycle of waste backwash water in ultrafiltration drinking water treatment processes

Research Article| June 01 2011 Recycle of waste backwash water in ultrafiltration drinking water treatment processes Stephanie Leah Gora; Stephanie Leah Gora 1Department of Civil and Resource Engineering, Dalhousie University, 1360 Barrington St, Bldg D, Rm D215, Halifax, Nova Scotia B3J 1Z1, Canada Search for other works by this author on: This Site PubMed Google Scholar Margaret Evelyn Walsh Margaret Evelyn Walsh 1Department of Civil and Resource Engineering, Dalhousie University, 1360 Barrington St, Bldg D, Rm D215, Halifax, Nova Scotia B3J 1Z1, Canada E-mail: mwalsh2@dal.ca Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2011) 60 (4): 185–196. https://doi.org/10.2166/aqua.2011.050 Article history Received: August 16 2010 Accepted: November 16 2010 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Stephanie Leah Gora, Margaret Evelyn Walsh; Recycle of waste backwash water in ultrafiltration drinking water treatment processes. Journal of Water Supply: Research and Technology-Aqua 1 June 2011; 60 (4): 185–196. doi: https://doi.org/10.2166/aqua.2011.050 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex In drinking water treatment, ultrafiltration (UF) membrane systems are generally operated at 90 to 95% recovery with production losses resulting from waste residual streams such as backwash water and clean-in-place (CIP) liquid residuals. In drought-prone regions, it may be desirable to apply alternative UF plant design configurations to increase recovery rates and minimize water loss. This approach could consist of adding a secondary stage UF membrane for treatment of first stage UF residuals, or recycling the first stage UF waste residuals by blending a percentage of the backwash water with the raw water at the front of the treatment train. For small systems, the second option may present a more cost-effective solution. The overall objective of this research project was to investigate the potential impacts to UF permeate water quality and coagulation pretreatment efficacy in a bench-scale submerged UF membrane system operating with and without waste backwash water recycle. The results of the study showed that blending 10% waste backwash water with raw water did not negatively impact UF permeate water quality. The results also demonstrated that recycling waste backwash water prior to coagulation–UF treatment may improve organic removal and reductions in neat coagulant dosage may be possible to achieve specific DBP precursor removal targets. coagulation, filter backwash water, natural organic matter, ultrafiltration This content is only available as a PDF. © IWA Publishing 2011 You do not currently have access to this content.

Effect of coagulation mechanism on membrane permeability in coagulation-assisted microfiltration for spent filter backwash water recycling

Coagulation is an effective pre-treatment process in membrane filtration for recycling spent filter backwash water (SFBW). To optimize the operation of the coagulation/filtration process for SFBW recycling, it is important to understand the critical role of coagulation mechanism on membrane filtration. In this study, SFBW samples were coagulated with polyaluminum chloride (PACl), followed by a dead-end microfiltration (MF), and the mean permeate flux and permeate quality were determined. The results showed that pre-coagulation improved the flux decline and the degree of the improvement was closely related to coagulation mechanisms. The permeate flux was enhanced most effectively by precipitation charge neutralization (PCN) coagulation, followed by charge neutralization and then sweep flocculation. Close examination of cake properties indicated that the reduced cake resistance ( R c ) was subjected to the coagulated SFBW flocs in response to different coagulation mechanism. Smaller flocs, induced by PCN, were more compact and stronger, forming less compressible cake, which facilitated membrane filtration, while slower membrane filtration was observed when more compressible cake formed from larger flocs of looser and weaker structure. Coagulation mechanism also governed the size distribution of SFBW floc, which is strongly related to the subsequent cake compressibility as well as membrane permeability in membrane filtration.

Ceramic membranes for water treatment

Ceramic membranes, different in pore size and membrane material, were applied to remove particulate and dissolved matter from different spent filter backwash water types as well as from dam water. The study was conducted in pilot scale under conditions typical for waterworks at a dam water treatment plant. A comparison of different ceramic membranes implied that total membrane resistance was more influenced by feed water type and by operation than by membrane type for the waters tested. Nevertheless, ceramic membranes seem to accumulate during operation less organic foulants especially polysaccharides compared to organic membranes leading to lower total membrane resistances for ceramic membranes during filtration process. Ceramic membranes may be considered to be applicable to treat spent filter backwash water as well as source water in public water supply.

Evaluation of an emerging water treatment technology: ceramic membranes

Historically, low-pressure membranes (microfiltration (MF) and ultrafiltration (UF)) used in potable water treatment are made of polymers (polysulfone (PS), polypropylene (PP), polyethersulfone (PES), polyvinylidene fluoride (PVDF) etc). Recently, membranes made of ceramic materials (aluminium oxide) have been developed by MetaWater (Japan), Kubota (Japan) and others and is being marketed in the United States (US) by Krüger, Inc. (Cary, NC). Ceramic membranes offer several potential advantages over polymeric membranes, including higher mechanical robustness and ability to handle higher loading of particulates, higher resistance to oxidants and membrane cleaning chemicals, higher membrane integrity, longer service life and compact footprint. The authors conducted collaborative evaluations of this emerging technology at two different places; (i) Elm Fork Water Treatment Plant (WTP) of Dallas Water Utilities (DWU), Dallas, Texas, USA and (ii) Graham Mesa WTP, City of Rifle, Rifle, Colorado, USA. The evaluations included pilot testing of ceramic membranes in direct filtration mode (i.e. without clarification) and with coagulant addition. The water streams that were pilot tested at Elm Fork WTP included Trinity River water, spent filter backwash wastewater and lagoon recycle water (spent filter backwash water combined with clarifier blow down water). The City of Rifle pilot testing was conducted on Colorado River water. This paper presents the key results of these two pilot studies. Results of pilot testing were used to define the potential membrane flux, backwash protocols (interval and duration), chemical enhanced backwash (CEB) and clean-in-place (CIP) protocols. Pilot test results and engineering judgment were used for developing concept-level sizing and outlining parameters for future evaluation. This paper will discuss the key technical and economic considerations of the emerging treatment technology and its potential applications for potable water treatment. This paper will be of interest to water providers that are considering alternatives to treat challenging source waters (waters with high particulates and under heavy microbial influence), build new compact water treatment plants, increase plant capacity through membrane retrofits and treat recycle streams at existing WTPs.

Disinfection by-products in filter backwash water: Implications to water quality in recycle designs

The overall purpose of this research was to investigate disinfection by-product (DBP) concentrations and formation potential in filter backwash water (FBWW) and evaluate at bench-scale the potential impact of untreated FBWW recycle on water quality in conventional drinking water treatment. Two chlorinated organic compound groups of DBPs currently regulated in North America were evaluated, specifically trihalomethanes (THMs) and haloacetic acids (HAAs). FBWW samples were collected from four conventional filtration water treatment plants (WTP) in Nova Scotia, Canada, in three separate sampling and plant audit campaigns. THM and HAA formation potential tests demonstrated that the particulate organic material contained within FBWW is available for reaction with chlorine to form DBPs. The results of the study found higher concentrations of TTHMs and HAA9s in FBWW samples from two of the plants that target a higher free chlorine residual in the wash water used to clean the filters (e.g., clearwell) compared to the other two plants that target a lower clear well free chlorine residual concentration. Bench-scale experiments showed that FBWW storage time and conditions can impact TTHM concentrations in these waste streams, suggesting that optimization opportunities exist to reduce TTHM concentrations in FBWW recycle streams prior to blending with raw water. However, mass balance calculations demonstrated that FBWW recycle practice by blending 10% untreated FBWW with raw water prior to coagulation did not impact DBP concentrations introduced to the rapid mix stage of a plant’s treatment train.

Recycling of spent filter backwash water using coagulation-assisted membrane filtration: effects of submicrometre particles on membrane flux

Membrane separation technology has been widely used for recycling of spent filter backwash water (SFBW) in water treatment plant. Membrane filtration performance is subject to characteristics of the particles in the SFBW. A bench-scale microfiltration (MF) coupled with pre-coagulation was set up to evaluate the recovery efficiency of SFBW. Effect of particle size distribution and zeta potential of the coagulated SFBW on the membrane filtration as well as the coagulation strategies were investigated. Pore clogging was more severe on the membrane with 1.0 mum pore size than on the membrane with 0.5 mum pore size due to the fact that submicrometre particles are dominant and their diameters are exactly closed to the pore size of the MF membrane. Pre-settling induced more severe irreversible fouling because only the submicrometre particles in the water become predominant after settling, resulting in the occurrence of more acute pore blocking of membrane. By contrast, pre-coagulation mitigates membrane fouling and improves membrane flux via enlarging particle size on membrane surface. The variations of zeta potential in response to coagulant dosing as well as fractal dimension were also compared with the performance of the subsequent filtration. The result showed that pre-coagulation induced by charge neutralization at the optimum dosage where the zeta potential is around zero leads to the optimal performance of the subsequent membrane filtration for SFBW recycling. At such condition, the fractal dimension of coagulated flocs reached minimum.

Recirculação de água de lavagem de filtros e perigos associados a protozoários

Apresentam-se, neste trabalho, os resultados (i) da caracterização da água de lavagem de filtros (ALF) da estação de tratamento de água da Universidade Federal de Viçosa (ETA- UFV); (ii) de ensaios de clarificação da ALF em colunas de sedimentação, com e sem uso de polímeros; (iii) de ensaios de recirculação de ALF em ETA piloto (EP), sob condições variadas de razão de recirculação (5 a 20% de incremento de vazão) e de turbidez da mistura de água bruta (AB) com ALF (12,1 a 257,3 uT). Na ALF foram encontradas concentrações em ordem de grandeza de 10¹ cistos de Giardia spp. e oocistos de Cryptosporidium spp. por litro. Os resultados dos ensaios em coluna de sedimentação e de recirculação na EP demonstraram que a clarificação da ALF com uso de polímeros contribui para a minimização de perigos associados à introdução de cistos de Giardia e oocistos de Cryptosporidium.

Treatment Spent Filter Backwash Water using Dissolved Air Flotation (DAF) in Isfahan WTP

Recovering spent filter backwash water is currently receiving a great deal of attention. EPA published the Filter Backwash-Recycling Rule (FBRR) in 2001. Recycle stream may contain significant concentration of pathogens, such as, cryptosporidium and Giardia. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation technology. In this study with using a pilot of DAF effluent turbidities of >20NTU could be easily obtained, when raw water turbidities were in excess of 800 NTU. Chemical requirements were low with only a single low dose of polyaluminium chloride (PACl) required binding the floc particles to form a solids matrix suitable for flotation. The results showed that the efficiency of continuous flow DAF with using PACl as coagulant for removal of Turbidity, COD, HPC, SS and MPN were 97, 72, 75, 95 and 100 percent, respectively. The statistical analyses indicated that the optimum saturation pressure is 4-5 atm, during recycle rate of 20-25 percent. The removal efficiencies of turbidity and bacteria in coagulation with sedimentation were reported up to 70 and 65 percent, while in this study using DAF with coagulant PACl could remove turbidity, COD, SS and bacterial up to 97,72, 95 and, 72 percent respectively.

Impact of recycling filter backwash water on organic removal in coagulation–sedimentation processes

The overall purpose of this research was to examine the impacts of filter backwash water (FBWW) and membrane backwash water (MBWW) recycles on water quality in coagulation–sedimentation processes. Specifically, the impact of recycling 5 or 10% by volume of FBWW and MBWW with surface water on the removal of natural organic matter (NOM) was evaluated at bench-scale using a standard jar-test apparatus and measurement of specific water quality parameters including total organic carbon (TOC), dissolved organic carbon (DOC), UV254, turbidity, total aluminum and zeta potential. The results of jar test conducted on a source water with a specific UV absorbance (SUVA) value within the range of 2–4 mg/L m showed a significantly higher removal of DOC from the raw water that was blended with 5 and 10% by volume of FBWW as compared to control trials where backwash water was not added. Increasing rates of MBWW that did not contain destabilized hydroxide precipitates did not significantly change DOC concentrations in the settled water samples as compared to the control trials. For source waters that are characterized as having low turbidity with medium SUVA values, these results could hold particular significance for plants that have reached treatment ceilings in terms of dissolved NOM removal using conventional coagulation designs.

Characterization of Hazardous Organics in Impounded Source Waters and Filter Backwash Water (High Veldt), South Africa

Characterization of Hazardous Organics in Impounded Source Waters and Filter Backwash Water (High Veldt), South Africa

Wash water in waterworks: contaminants and process options for reclamation

Reclamation of clean water from filter backwash water was studied through pilot-scale experiments. The pilot plant consisted of clarification, sand-filtration, and ultrafiltration modules in sequence, with a provision to bypass the sand filter. Clean water that conformed to World Health Organization (WHO) guidelines on Potable Quality was reclaimed. Turbidity, aluminum and iron were found to be critical contaminants in process selection and design. Clarification, followed by sand filtration, was found to be the minimum requirement for recycling filter backwash. However, membrane filtration would enhance reclaimed water quality as the membrane acts as an additional barrier against Giardia and Cryptosporidium.

Strategic pathways for the sustainable management of water treatment plant residuals

In North America, the rapid movement away from the direct discharge of water treatment plant (WTP) residual streams to receiving environments has resulted in considerable benefits to the drinking water industry in terms of enhancing environmental stewardship practices and supporting source water protection strategies. Over the past 20 years, application based research on appropriate technologies to treat residual streams such as filter backwash water (FBWW) has promoted the development of integrated process design that presents recycling as a viable residual management option. However, as utilities continue to develop and expand their main process lines to comply with more stringent government regulations encompassing both water quality and residual disposal practices, the development of sustainable residual management practices is expected to become a more prominent issue for this industry. The purpose of this paper is to present, from a critical point of view, the matrix of issues that currently exist regarding WTP residual streams and strategic pathways that would enhance future decision making processes for achieving long-term residual management solutions for the drinking water industry.

Application of submerged membranes for the treatment of spent filter backwash water

The application of membrane filtration in the treatment of spent filter backwash water (SFBW) permits efficient removal of microorganisms, suspended particles and organic substances, depending on the used membrane molecular weight cut-off. However, flux decline, due to deposits and adsorption of substances (salts, colloids, organics, particles, microorganisms, etc.) tends to limit the use of membranes. Characterization of SFBW samples from different waterworks showed that three major factors contribute to the SFBW properties: the raw water itself, the time interval of sand filter operation and additional treatment steps. The main differences between SFBW samples were found principally in DOC, TOC and turbidity. Experiments with submerged membranes (lab- and pilot- scale modules) showed that there was a clear correlation between DOC concentration of the feed and the flux decline: when the DOC-concentration increased, the flux decline increased. Additionally, the presence of calcium led not only to an important flux decline but to high adsorption of NOM on the membrane surface. Iron concentrations in the micromolar range resulted in a considerably decline of flux. Filtration of SFBW revealed that the decline of permeability is mainly determined by DOC, calcium and iron concentrations. A decisive effect of biofouling on membrane performance is expected for long term experiments.

Biostability and disinfectant by-product formation in drinking water blended with UF-treated filter backwash water

The overall objective of this study was to investigate the impact of blending membrane-treated water treatment plant (WTP) residuals with plant-filtered water on finished water quality in terms of biostability and disinfectant by-product (DBP) formation. Filter backwash water (FBWW) was treated with a pilot-scale ultrafiltration (UF) membrane to produce permeate that was blended with plant-finished water. The batch studies involved storing samples for a specified time with a disinfectant residual to simulate residence time in the distribution system. Both chlorinated and non-chlorinated FBWW streams were evaluated, and the experimental design incorporated free chlorine, monochloramine, and chlorine dioxide in parallel to a model system that did not receive a disinfectant dose. The results of the study found that blending 10% UF-treated FBWW with plant-filtered water did not have an impact on water biostability as monitored with heterotrophic plate counts (HPCs) or DBP concentrations as monitored by TTHM and HAA5 concentrations. However, the presence of preformed THM and HAA species found in chlorinated FBWW streams may result in higher levels of initial DBP concentrations in blended water matrices, and could have a significant impact on finished water quality in terms of meeting specific DBP guidelines or regulations.

Ultrafiltration for the reuse of spent filter backwash water from drinking water treatment

During most water treatment processes, spent filter backwash water (SFBW) is generated. Reuse of SFBW is of concern because of the possible recycling of heavy metals, precursors for disinfection by-products and microorganisms. Innovations in membrane technology, especially in micro- and ultrafiltration processes, offer a suitable treatment for SFBW in order to guarantee a water quality necessary for reuse. Results from a pilot-scale ultrafiltration plant with submerged membranes are presented. Experiments were performed with SFBW from a full-scale water treatment plant. The plant was operated with high fluxes of more than 40 L/(m 2·h) using clarified and non-clarified SFBW. Best membrane performance was obtained using non-clarified SFBW. As a result, no space- and timeconsuming sedimentation processes are necessary. The presence of powdered activated carbon in the SFBW did not have a negative impact on flux and TMP. Results confirmed that the filtrate can be used as an additional and safe water source. When a continuous maintenance disinfection was provided, filtrate was free of microbial contamination and could be reused without any safety concerns.

Blending membrane treated WTP waste residuals with finished water: impacts to water quality and biofilm formation

The purpose of this study was to evaluate the impact of blending filtered water with treated waste residuals streams from a water treatment plant on finished water quality and biofilm formation in a modelled distribution system. A mixed waste residual stream composed of an equalized blend of filter backwash water (FBWW) and clarifier sludge blowdown was treated with a pilot-scale ultrafiltration (UF) membrane. The UF treated residuals stream was blended with plant finished water to model a recycle return location to the clearwell of a drinking water treatment train. Field evaluations involved the use of bench-scale annular reactors (ARs) to investigate two parallel model distribution systems: (i) a control system representing 100% plant filtered water (AR-filtered) and (ii) a blended system representing 10% by volume of the UF permeate blended with plant filtered water (AR-blended). To evaluate the impact of chemical disinfection on bacterial regrowth and the fate of inorganic constituents, free chlorine, monochloramine and chlorine dioxide were fed to the ARs during three distinct disinfection trials. An initial disinfection trial consisted of a control run during which no disinfectant was added. The results of the field experiments showed that blending 10% by volume of the UF permeate with plant finished water did not significantly impact regrowth of heterotrophic bacteria in the bulk or biofilm phases. Throughout each disinfection trial, the largest difference in HPCs noted between the two systems was 1 log in the bulk and biofilm samples. Free chlorine and monochloramine disinfection resulted in the greatest mitigation of microbial biofilm in both AR-filter and AR-blended systems. Aluminum, manganese, and iron in the bulk phase were found to be below Canadian Drinking Water Guideline levels. However, the detection of manganese-oxidizing bacteria (MOB) and elevated manganese in biofilm samples from AR-blended could hold potential implications for blending UF treated residual streams on biofilm development and inorganic post-precipitation occurrences in systems treating source waters containing elevated concentrations of manganese.

Application of a combined UF/RO system for the reuse of filter backwash water from treated swimming pool water

Results from the full-scale application of a combined ultrafiltration (UF) and reverse osmosis (RO) treatment process for the reuse of spent filter backwash water (SFBW) from treated swimming pool water are presented. Ultrafiltration treatment showed a significant reduction of particulate matter. Turbidity decreased from values between 5 and 25 FNU in the feed (SFBW) to values below 0.02 FNU. At the plant investigated in this study, filtration periods up to 90 min were achieved. With this configuration, efficiencies of more than 97% for the UF plant were obtained. In order to avoid an increasing concentration of salts and dissolved compounds, up to one-third of the UF filtrate was directed to the RO plant. As a result, no deterioration of the swimming pool water quality was observed, and especially the concentration of disinfection by-products did not increase. A cost comparison showed annual savings depending on the expected useful life of the membranes. If the expected useful life of the membranes exceeded 7 years, annual savings of more than 4,300 would be possible. With regard to threshold values for the direct discharge of the concentrate, the concentration of suspended solids, adsorbable organic halides as well as the chemical oxygen demand are of special interest.

Detection of Cryptosporidium oocysts and Giardia cysts in swimming pool filter backwash water concentrates by flocculation and immunomagnetic separation

The purpose of the present study was to evaluate techniques for detection of Giardia cysts and Cryptosporidium oocysts in swimming pool filter backwash water. Calcium carbonate flocculation was used for water samples concentration of 1 l filter backwash water samples. Immunomagnetic separation (IMS) was used for separation of cysts and oocysts from detrital material. Cysts and oocysts were then detected using direct immunofluorescence. ColorSeed C&G™ was used as an internal standard. Recoveries were examined at several processing points. Highest recoveries (23% Cryptosporidium, 18% Giardia) were obtained using lower filter backwash volumes, greater IMS volumes, and addition of Tween20™ to backwash samples prior to processing. The combination of CaCO3 flocculation, IMS and direct immunofluorescence was found to be an effective tool for the detection and quantification of Giardia spp. and Cryptosporidium spp. in filter backwash water samples.